Dual mode wireless data communications

ABSTRACT

A dual mode mobile unit is arranged to communicate in either a first or second data communications standard, such as combined Bluetooth and 802.11 operation. An interface unit converts received Bluetooth or 802.11 format signals into 802.11 frame format data signals to be provided to a digital signal processor which is programmed to process signals in either standard. The dual mode mobile unit can operate in the 802.11 standard to reserve a time interval for Bluetooth activity during which other 802.11 units will avoid transmissions to avoid interference.

BACKGROUND OF INVENTION

One of the current techniques for providing a wireless local areanetwork which has achieved widespread use, is international standardIFO/IEC standard 8802-11, which is also ANSI/IEEE Standard 802.11(herein Standard 802.11). This standard provides a uniform specificationfor a wireless local area network media access control (MAC) andphysical layer (PHY) so that equipment from multiple sources workstogether.

The 802.11 standard is useful for wireless local area networks which maybe used in a facility, such as a store, a factory, a research laboratoryor a university for providing wireless communication between astationary system, such as a wired network or a computer and mobileunits. The wired network includes one or more access points whichinterfaced the wired network or computer to the mobile units using radiosignals. The mobile units, which may include portable computers having awireless radio add-on, personal digital assistants, bar code scanners,point of sale devices and the like, communicate with the access point toprovide wireless access to the underlying system.

There is currently being developed a specification for the “BluetoothSystem” for providing wireless communication over a shorter range, forexample providing communication between a portable personal computer anda printer or other devices. The Bluetooth specification is intended toprovide less expensive radio protocol technology for communicating overshorter ranges. The draft Bluetooth specification is available atwww.Bluetooth.com.

Both the 802.11 system and the Bluetooth system operate in the same 2.4GHz ISM radio frequency band. The devices in both systems are mobile,and may radiate spread spectrum signals over the frequency range.Accordingly, there is a possibility of the signals from one systeminterfering with transmissions in the other system and causing loss ofdata. Also, for many applications it is desirable for a mobile unit tobe able to use both systems.

It is an object of the present invention to provide a dual mode mobileunit capable of operating in both the 802.11 system and in a Bluetoothsystem for communications between the dual mode mobile unit and otherunits using either system.

It is a further object of the invention to provide methods whereby802.11 systems and Bluetooth systems can co-exist without signalinterference.

SUMMARY OF THE INVENTION

In one aspect of the invention there is provided a method for operatinga dual mode mobile unit arrange to transmit and receive signalsoperating using first and second wireless protocols, such as IEEE 802.11protocol and the Bluetooth protocol. The mobile unit is operated underthe first wireless protocol. The mobile unit uses the first wirelessprotocol to reserve a transmission time interval in a frame of the firstwireless protocol for purposes of operating under the second wirelessprotocol. During the reserved time interval the mobile unit operatesunder the second wireless protocol to send and receive signals.

In a preferred arrangement, where the first wireless protocol includesrequirements for a transmission using that protocol for holding areserved time, the mobile unit may transmit short transmissions of underthe first wireless protocol at the beginning and the end of the reservedtime interval.

In one arrangement the dual mode mobile unit operates as a master unitin the second wireless protocol to control the operation of at leastslave unit that operates in the second wireless protocol. The dual modeunit can reserve a transmission time interval in a frame of the firstwireless protocol and control the slave unit using the second wirelessprotocol to transmit during the reserved time interval.

Preferably the process of reserving transmission time in the firstwireless protocol is repeated at a selected data cycle, which may bealtered according to the level of radio activity using the secondwireless protocol.

In accordance with the invention there is provided a method foroperating a dual mode mobile unit including providing a firsttransmitter and a first receiver for operating using a first wirelessprotocol for sending and receiving signals. The first transmitterresponds to first protocol baseband signals and the first receiverprovides output first protocol baseband signals. A second transmitter isprovided for operation using a second wireless protocol and responsiveto second protocol baseband signals, and a second receiver is providedfor operating using the second wireless protocol providing output secondprotocol baseband signals. A digital processor is programmed to processsignals for both the first and the second protocols. The processor isresponsive to receive digital signals in a first protocol frame andprovides output digital transmission signals in the first protocol frameformat. The output first and second protocol baseband signals from thereceivers are converted to received digital signals in the firstprotocol frame format for the digital processor. The output digitaltransmission signals in the first protocol frame format are converted tofirst or second protocol baseband signals for the respective first orsecond transmitter.

In accordance with the invention there is provided a dual mode mobileunit for operating according to first and second wireless protocols. Thedual mode mobile unit includes first and second RF modules respectivelyfor transmitting and receiving signals according to first and secondwireless protocols and each responsive to baseband signals fortransmission and providing output baseband signals on reception. Thereis provided a digital processor responsive to received digital signalsand digital data signals to be transmitted for processing the digitalsignals according to one of the first and second protocols. An interfaceunit is provided for converting received baseband signals from the firstand second RF modules and supplying corresponding digital signals to theprocessor and for receiving digital signals from the processor andsupplying first and second corresponding baseband signals to betransmitted by the first and second RF modules respectively.

In a preferred arrangement the processor controls the interface unit tosend and receive signals to and from the first and second RF modules. Ina preferred arrangement the interface unit receives output basebandsignals from the second RF module and supplies corresponding digitalsignals to the digital processor in a first protocol frame format andreceives digital signals from the digital processor in the firstprotocol frame format and supplies corresponding baseband signals to thesecond RF module according to the second wireless protocol.

For a better understanding of the present invention, together with otherand further objects, reference is made to the following description,taken in conjunction with the accompanying drawings, and its scope willbe pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the communications portion of a dualmode mobile unit according to the present invention.

FIG. 2 is a graph showing one embodiment of the method of the inventionduring a frame according to standard 802.11 practice.

FIG. 3 is a diagram showing communications between mobile units usingfirst and second wireless communication protocols.

FIG. 4 is a diagram showing another configuration of mobile units forcommunication between mobile units using two wireless transmissionprotocols.

FIG. 5 is a flow design illustrating operation of configurable bitstream processor 42 for receive operations.

FIG. 6 is a flow design illustrating operation of configurable bitstream processor 42 for transmit operations.

DESCRIPTION OF THE INVENTION

Referring to FIG. 3, there is shown a configuration of a wireless localarea network 100, which is operating under a first wireless protocol,such as standard 802.11 for providing a wireless local area network,which may extend over an entire business, educational or researchfacility. In the first wireless network 100 there is provided one ormore access points 102, which may be interconnected with a host computerand provide wireless data communications to all or a portion of thefacility. Typically, wireless devices using standard 802.11 cancommunicate with access points at a range up to about 30 meters,depending on the building configuration and the multi-path environment.In larger facilities, multiple access points are usually provided andthe multiple access points may be interconnected to a host computer andto each other using a wired data network. The wireless local areanetwork 100 shown in FIG. 3 includes a dual mode mobile unit 10 which isarranged to communicate with the access point 102 using the 802.11standard and also to communicate with other units 108 using a secondwireless communication standard, such as the Bluetooth standard. Dualmode mobile unit 10 may, for example, communicate with printer 106 usingthe Bluetooth standard. It may also communicate with the access point102 using the 802.11 standard and with other mobile unit 108 which is ina Bluetooth piconet 110 using the Bluetooth standard. The drawing alsoshows another Bluetooth piconet 115 having units 112 and 114communicating with each other without interference with wireless localarea network 100.

The present invention addresses the problem of interference that mightoccur between the communications of mobile unit 10 with access point 102using the 802.11 standard and communications being carried on byBluetooth unit 108 using the Bluetooth standard. According to apreferred embodiment of the invention, mobile unit 10 is arranged tocommunicate using both standards and to coordinate communications usingthe Bluetooth standard with the communications using the 802.11standard.

A block diagram of mobile unit 10 is shown in FIG. 1. The communicationsportion of mobile unit 10 includes an RF module 12 for providing radiocommunications using the 802.11 standard and a second RF module 14 forproviding radio communication using the Bluetooth standard. There isadditionally provided an communications processing module 16 and adigital processor module 18. RF module 12 includes a transmitter 22 anda receiver 24, both connected to antenna 26. The transmitter 22 respondsto baseband signals provided from module 16 via the WLAN radio interface34. Transmission baseband signals and received baseband signals aredemodulated and modulated by 802.11 baseband modem 38, which, as anexample, may be an Alantro modem. Interface 34 and modem 38 areconventional 802.11 modules.

Communications processing module 16 is also connected to RF module 14which includes Bluetooth transmitter 28 and Bluetooth receiver 30 whichare connected to antenna 32. It should be recognized that a singleantenna may be provided for both RF modules, and may be switched betweenthe modules according to the current operation.

Communications processing module 16 includes a Bluetooth radio interface36 and Bluetooth baseband modem 40, again following the standards of theBluetooth systems.

Modems 38 and 40 are connected to configurable bit-stream processor 42which receives the 802.11 and Bluetooth baseband signals, strips theoverhead data, computes the CRC and provides the message data to firstin and first out (FIFO) memory 44 as digital data signals. Receivedbaseband signals from modem 40 are also processed to provide them in theframe format of 802.11 data which is likewise provided to FIFO memory44.

Configurable bit-stream processor 42, which may be a programmed fieldprogrammable logic array is arranged to process the serial bit streamsfor both the Bluetooth and 802.11 communications. One configuration forreceiving signals is shown in FIG. 5, wherein there is provided amultiplexer 160 for connection to the 802.11 and Bluetooth modem receivechannels. The receive operation is controlled by a finite state machine162 which controls the logic elements according to the communicationformat, and likewise controls multiplexer 160, as indicated by dottedlines. Serial to parallel converter 164 receives the header data andconverts it to parallel data which is stored in registers 166, where iscan be accessed by state machine 162. The received bit stream islikewise provided to a frame synchronization detector 168 and receivedCRC data is provided to CRC register 170, which are likewise accessed bystate machine 162. The data stream is additionally provided tounscrambler 172, CRC module 174, which performs the CRC check againstthe received CRC header and serial to parallel converter 176 whichprovides the received data to FIFO storage 44.

FIG. 6 shows the logic operation of an example of configurablebit-stream processor for operation in the transmit mode. Finite statemachine 180 is configured to generate the frame header, which isprovided to register 192 and converted to serial form in parallel toserial converter 194. Frame sync is generated in generator 188 and CRCis computed and provided to CRC header register 190. Data to betransmitted is read from FIFO 44 by parallel to serial converter 182,and CRC is computed in CRC logic 184. Forward error correction isgenerated in logic 186. State machine 180 controls the logic units toprovide the entire transmit packet in appropriate order to OR gate 195and the packet is routed as the complete bit stream in the appropriateformat to the transmit circuits of either the 802.11 modem 38 or theBluetooth modem 40 by multiplexer 196.

Interface 46 clocks the signals for both the 802.11 and Bluetoothsignals to interface 50 in digital processor 18. Both the 802.11 datasignals and the Bluetooth data signals are provided in 802.11 frameformat and loaded into random access memory 58 in digital processor 18.Digital processor 18 includes a processor 56, such as an ARC or ARMmicroprocessor and flash memory 20 which contains programs for MAC leveldigital processing of both 802.11 signals and Bluetooth signalsencapsulated in 802.11 frame format, and provides the output messagedata signals to host interface 52 for transmission to host 60. Likewisesignals from the host processor 60 are converted into the frame formatof 802.11 standard in digital processor 18 and provided throughinterface 50 to the communications processing module 16. Digital signalsto be transmitted, which are provided to module 16 in 802.11 frameformat are stored in FIFO memory 44 and provided to circuit 42. Circuit42 computes and adds the CRC check data for either 802.11 or Bluetoothformat. If the signals are to be transmitted in 802.11 format they areprovided to modem 38 which provides a modulated baseband signal to WLANradio interface 34 for transmission. If the signals are to betransmitted in Bluetooth format circuit 42 removes the 802.11 frameformat and provides a data bit stream in Bluetooth format to Bluetoothbaseband modem 40 which provides a baseband signal to Bluetooth radiointerface 36 for transmission by transmitter 28.

It should be recognized by those skilled in the art that as analternative to converting Bluetooth message data to 802.11 frame formatin circuit 42, 802.11 message data may be converted to and fromBluetooth frame format in circuit 42.

FIG. 2 is a time flow diagram corresponding to an 802.11 frame whichindicates the preferred operation of the dual mode unit 10 of FIG. 1, orother dual mode mobile unit, in connection with coordinating Bluetoothoperations to avoid interference with 802.11 transmissions. Referring toFIG. 3, it is assumed that mobile unit 10 is associated with accesspoint 102 under 802.11 protocol. In order to provide a window foroperation under the Bluetooth protocol, dual mode mobile unit 10 sends arequest to send (RTS) signal 70 to access point 102. Access point 102acknowledges with a clear to send (CTS) signal 72 providing a timeinterval for operation of a transmission from dual mode mobile unit 10.The CTS signal causes other mobile units, MU-a and MU-b, to set theirnetwork allocation vector (NAV) to a value indicating that the networkwill be busy during the transmission time interval requested by dualmode mobile unit 10. The dual mode mobile unit 10 thereafter sends ashort frame 802.11 message 74. This short frame message 74 is intendedto make other mobile units MU-a and MU-b believe that dual mode mobileunit 10 is sending a frame of data under Standard 802.11. Following thisshort frame 74, dual mode mobile unit 10 converts to Bluetooth operationas a master unit and sends a Bluetooth inquiry 75, which, for example,may be received by Bluetooth unit 108 which responds with a Bluetoothresponse 80. During a sub-time interval 82, unit 10 and unit 108 orother Bluetooth slaves will engage in Bluetooth communications which isfollowed by a Bluetooth standby signal 84. At the end of the timeinterval, which was reserved by dual mode mobile unit 10, dual modemobile unit 10 sends a final 802.11 short frame 86 indicating completionof its transmission. This provokes an acknowledgment signal 88 fromaccess point 102 which indicates according to the 802.11 protocol thatthe transmission has been completed. Thereafter the system continues innormal 802.11 operation. The sequence of interrupting 802.11 traffic forBluetooth activity may be repeated at a data cycle which can be selectedaccording to the 802.11 and Bluetooth radio activity.

An additional feature that is optionally provided by the configurationof the present invention is that the dual mode mobile unit 10 of thepresent invention, which controls the associated slave units in itspiconet, may signal the slave units at the end of the Bluetooth radioactivity (signal 84) to cause the slaves to enter a lower power“STANDBY” mode during the time the dual mode mobile unit undertakes802.11 communication. The duration of the standby mode may be set by themaster signal, may be fixed or may be ended by a renewal of Bluetoothactivity by the master.

Referring to FIG. 4, there is shown a configuration wherein a Bluetoothmessage from piconet 132 may be relayed by dual mode mobile unit 10Athrough its access point 102 to another dual mode mobile unit 10B andthereafter through a Bluetooth piconet 146 to another Bluetooth unit144. In the configuration of FIG. 4 dual mode mobile unit 10 a hasaccess to Bluetooth piconet 132 which contains Bluetooth units 134 and136. Dual mode mobile unit 10A is preferably arranged to commandBluetooth units 134 and 136 to act as slave units to dual mode mobileunit 10A. Once units 134 and 136 have been associated as slave units todual mode mobile unit 10A, communications by mobile units 134 and 136 iscontrolled by dual mode mobile unit 10A to occur at specific time frameintervals which have been reserved in 802.11 wireless local area network130 by dual mode mobile unit 10A. Specifically, referring to FIG. 2,dual mode mobile unit 10A reserves an 802.11 frame for Bluetoothactivity, as it would do in its own transmissions and thereafter byusing Bluetooth communication 75 instructs Bluetooth unit 134 or 136 tosend its Bluetooth transmissions during the following time intervals 80,82. Accordingly, 802.11 transmissions can be controlled to not occurduring the transmission intervals reserved for Bluetooth activity byeither unit 134, 136 or 10A.

The configuration of FIG. 4 also allows Bluetooth units 134 and 136 tosend messages to other Bluetooth units 142, 144 in a different Bluetoothpiconet 140 by way of two dual mode mobile units 10A and 10B. Inparticular, a data message from Bluetooth mobile unit 134 may be send todual mode mobile unit 10A. This message may be relayed using 802.11communication from mobile unit 10A through access point 102 to dual modemobile unit 10B. Thereafter dual mode mobile unit 10B following theBluetooth protocol can send the relayed message to Bluetooth mobile unit144 or 142. In this way, the operator of Bluetooth mobile unit 134 cancommunicate data to be printed by Bluetooth printer 142 when the mobileunit 134 is not within the same Bluetooth piconet as printer 142.

While there have been described what are believed to be the preferredembodiments of the present invention, those skilled in the art willrecognize that other and further changes and modifications may be madethereto without departing from the spirit of the invention, and it isintended to claim all such changes and modifications as fall within thetrue scope of the invention.

1. A method for operating a dual-mode mobile unit arranged to transmitand receive signals using first and second wireless protocols,comprising: operating said mobile unit under said first wirelessprotocol; reserving a transmission time interval in a frame of saidfirst wireless protocol; and operating said mobile unit under saidsecond wireless protocol during said reserved time interval.
 2. A methodas specified in claim 1 further comprising operating said mobile unit totransmit using said first wireless protocol during an initial portion ofsaid reserved time interval.
 3. A method as specified in claim 2 furthercomprising operating said mobile unit to transmit using said firstwireless protocol during a terminal portion of said reserved timeinterval.
 4. A method for operating a dual mode mobile unit as specifiedin claim 1, wherein said operating said mobile unit under said secondwireless protocol comprises operating said mobile unit under said secondwireless protocol to act as a master unit for at least one slave unitoperating under said second wireless protocol, reserving a transmissiontime interval in a frame of said first wireless protocol and controllingsaid slave unit using said second wireless protocol to transmit usingsaid second wireless protocol during said reserved time interval.
 5. Amethod as specified in claim 4 further comprising operating said mobileunit to transmit using said first wireless protocol during an initialportion of said reserved time interval.
 6. A method as specified inclaim 5 further comprising operating said mobile unit to transmit usingsaid first wireless protocol during a terminal portion of said reservedtime interval.
 7. A method for operating a dual mode mobile unit asspecified in claim 1 wherein said reserving transmission time isrepeated at a selected duty cycle.
 8. A method for operating a dual modemobile unit as specified in claim 7 wherein said selected duty cycle isvaried based on the activity of radio traffic using said second wirelessprotocol.
 9. A method for operating a dual mode mobile unit comprising:providing a first transmitter for operation using a first wirelessprotocol and responsive to first protocol baseband signals; providing afirst receiver for operation using said first wireless protocol andproviding output first protocol baseband signals; providing a secondtransmitter for operation using a second wireless protocol andresponsive to second protocol baseband signals; providing a secondreceiver for operation using said second wireless protocol and providingoutput second protocol baseband signals; providing a digital processorprogrammed to process signals for said first and second protocols,responsive to received digital signals in a first protocol frame formatand providing output digital transmission signals in said first protocolframe format; converting said output first and second protocol basebandsignals to said received digital signals in said first protocol frameformat; and converting said output digital transmission signals fromsaid first protocol frame format to said first or second protocolbaseband signals.
 10. A dual mode mobile unit for operating according tofirst and second wireless protocols, comprising: first and second RFmodules, respectively for transmitting and receiving signals accordingto first and second wireless protocols, and each responsive to basebandsignals for transmission and providing output baseband signals onreception; a digital processor responsive to received digital signalsfor processing said digital signals according to one of said first andsecond protocols; and an interface unit for receiving baseband signalsfrom said first and second RF modules and supplying correspondingdigital signals to said processor, and for receiving digital signalsfrom said processor and supplying first and second correspondingbaseband signals to said first and second RF modules respectively.
 11. Adual mode mobile unit according to claim 10 wherein said processorcontrols said interface unit to send and receive signals to and fromsaid first and second RF modules.
 12. A dual mode mobile unit accordingto claim 10 wherein said interface unit receives output baseband signalsfrom said second RF modules and supplies said corresponding digitalsignals to said digital processor in a first protocol frame format, andreceives digital signals from said digital processor in said firstprotocol frame format and supplies corresponding baseband signals tosaid second RF module according to said second wireless protocol.